Polyurethane stents are used when there is an obstruction to the flow of urine. Majority of the patients with such stents are at the risk of urinary tract infection and salt encrustation. The present study is aimed at analyzing the in-vitro encrustation of calcium oxalate and other salts in the presence of common uropathogens (E.coli and P.mirabilis) on films made from Tecoflex®, a commercial grade polyurethane. In the absence of uropathogens, sodium ions and ammonia favor calcium adsorption whereas magnesium ions greatly depress it, resulting in increased hydrophillicity of the stent. With E.coli, Mg ions enhance the encrustation of calcium, whereas the other salts decrease its deposition. In case of P.mirabilis, irrespective of the type of salt, it enhances calcium encrustation except in the presence of sodium ions. Adhesion of uropathogens to the stent surface was higher in the presence of bovine serum albumin. Understanding the dynamics between various salts and microorganism in the urine, and urine - stent interface would aid in designing stents that are inert, resist encrustation and biofilm formation.

Ureteral stents find wide application in urology. The majority of patients with indwelling ureteral stents are at an increased risk of urinary tract infection. Stent encrustation and its associated complications lead to significant morbidity. This review critically evaluates various polymers that find their application as ureteral stents with regard to various issues such as encrustation, bacterial colonization, urinary tract infections, and related clinical issues. A complete literature survey was performed, and all the relevant articles were scrutinized thoroughly. We discuss issues of encrustation=biofilm formation, new approaches to their testing, polymers currently available for use, new biomaterials, coatings, and novel ureteral stent designs, thereby providing a complete update on recent advances in the development of stents. Finally, we discuss the future of biomaterial use in the urinary tract.